In general there are three types of filter media used in swimming pool water filtration. These are sand and sand substitutes, which may be considered to be free particulate type filter media, and fixed cloth type media, namely leaf filters and cartridge filters. In different applications one or another medium is preferred by the pool installer and manufacturers have been required to manufacture and inventory more than one type of housing and accessories, (the housing and the accessories being all parts of the filter other than the medium contained therein and both being hereinafter referred to as the "filter structure") for containment of the filter medium. This effort may lead to excessive inventories if the market is other than as predicted for a given model and version of a filter structure, to increased manufacturing costs from model changeover and multiple manufacturing lines, and undue capital expense for manufacturing equipment.